1. Field of the Invention
The invention is concerned with the field of polymer chemistry and relates to elastomeric materials as are usable, for example, as an inner liner material for vehicle tires, and to the use thereof.
2. Discussion of Background Information
Modern vehicle tires are constructed from a number of components. The main component of the vehicle tire is what is referred to as the carcass, which is composed of a running band and of a fabric substructure acting as a stability support. On the inside of the carcass, an elastomeric layer referred to as an inner liner layer or inner liner is applied which is used to enclose as well as possible the tire gas introduced in tubeless vehicle tires, so that the tire gas enclosed between the rim and tire is, to the greatest possible extent, not able to diffuse to the outside through the material of the vehicle tire and can only do so very gradually. A lowest possible gas permeability of the inner liner is therefore desirable, particularly also because a decrease in pressure in the tire has a negative effect on both the rolling friction of the tire, and the increased fuel consumption associated therewith, and also on the driving safety and the durability of the tire. In addition, the inner liner is used to protect other tire components, such as the carcass and steel belt, against air and moisture.
As elastomer materials for inner liners, synthetic rubbers such as butyl rubber (IIR), chlorobutyl rubber (CIIR) or bromobutyl rubber (BIIR) are used which already exhibit low gas permeability. In some cases, these butyl rubbers are used blended with other diene rubbers in order to achieve an improvement of the mechanical properties or a cost reduction, for example. Furthermore, the gas permeability of the material can also be improved by blending filler particles into the rubber matrix. Particularly the admixture of lamellar particles, such as layered silicates or graphenes, for example, reduces the gas permeability of the material as a result of a lengthening of the diffusion path of the gas molecules (tortuosity).
According to US 2006/0229404, a method for producing an elastomer blend is known in which, from an elastomer with expanded graphite, diene monomers are polymerized in the presence of 10 phr or more (parts per 100 parts rubber) of expandable graphite, so that the elastomer is intercalated into the graphite.
Also, a rubber composition for the production of inner tubes in refrigerant hoses is known from U.S. Pat. No. 6,548,585. The rubber composition is made from a brominated copolymer rubber, which can be poly[isobutylene-co-p-methylstyrene] (BIMSM), for example, and an inorganic lamellar filler, which can be graphite, zirconium phosphate, chalcogenides, talc, kaolinite, bentonite, montmorillonite, mica or chlorite, for example.
According to US 2010/0036023, elastomer materials made of graphitic nanoparticles, which are preferably graphene nanoparticles, are known. Elastomer materials of this type are used as inner liners in tire tubes.
Furthermore, from US 2005/0215693, a method is known by means of which the vulcanization properties of layered silicate/rubber systems are to be improved. In this method, the layered silicate is exfoliated by the addition of an ionic liquid and subsequently added to the rubber blend. The surfactant ionic liquid compatibilizes the layered silicate with the rubber and reduces the gas permeability thereof with no significant negative effect on the vulcanization properties.
An ionic liquid is generally understood as meaning a liquid which is composed exclusively of ions. Unlike the conventional term “molten salts,” which normally denotes a highly viscous and usually very corrosive medium with a high melting point, ionic liquids are already liquid at low temperatures (<100° C.) and have relatively low viscosity (DE 102 43 181 A1). Although ionic liquids have already been known since 1914, they were only studied intensively as a solvent and/or catalyst in organic systems in the last 10 years (overview article by K. R. Seddon in J. Chem. Technol. Biotechnol. 68 (1997), 351-356).
From U.S. Pat. No. 7,572,855 B2, a nanocomposite is also known which contains a cationic compatibilizer. The cationic compatibilizer is composed of a hydrophobic group and a heterocyclic cationic unit. In the case of rubber materials and tire materials, this nanocomposite can be used to achieve improved gas permeability, improved vulcanization properties and/or improved mechanical properties.